Caterpillar Pests Beware: New
Fungal Strain is Out to Get You

The discovery of beneficial fungi
that produce mycoinsecticides brightens the future of environmentally friendly
controls for insect crop pests, Agricultural
Research Service scientists report.

Mycoinsecticides are fungal sprays. When applied to insect-infested plants,
fungal spores attack the pests by penetrating their outer cuticle. Then the
fungus eats them from the inside out. Spores from dead insects can survive to
reinfect subsequent pest generations.

For example, one new strain of the Beauveria bassiana fungus--known
as BB-1200-- appears to be more effective in curbing caterpillar pests than its
close relative, the commercially available GHA strain.

Long-standing collaborations between ARS scientists at the U.S.
Plant, Soil and Nutrition
Laboratory, Ithaca, N.Y., and Mycotech Corp., Butte, Mont., led to the
discovery that spores of Beauveria strain GHA can control many important
insect pests of agricultural crops like cabbage, broccoli, cucumber and
greenhouse ornamentals. This discovery led to developing the commercial
products Mycotrol and BotaniGard, which have been registered for use in the
United States, Mexico, and other counties for biological control of
grasshoppers, whiteflies, aphids, thrips and diamondback moths.

After GHAs discovery, the search intensified for a more virulent,
broad-spectrum mycoinsecticide effective against a large group of lepidopteran
(caterpillar) pests. In June 1999, scientists in ARS fungal-screening
program at Ithaca discovered the high virulence and exceptionally broad
lepidopteran host range of the new Beauveria BB-1200 strain, originally
taken from a diamondback moth.

Laboratory bioassays showed BB-1200 consistently exhibited virulence equal
to or greater than the GHA strain against all lepidopteran pests tested.
Included were fall armyworm, beet armyworm, black cutworm, corn borer and
cabbage looper--pests not highly susceptible to GHA. These lepidopteran
defoliators are among the most destructive pests of important crops like corn
and cabbage, costing several billion dollars in losses each year.